The invention pertains to a universal motion control which functionally combines the classical tasks of a programmable logic controller and a numerical controller.
It is common today to model different hierarchical run levels both for programmable logic control and also for motion control, wherein the software tasks of the run levels are allocated to control a corresponding technical process. These tasks can comply with system tasks, but they can also be user-programmed.
From DE 197 40 550 A1 it is known that process control functionalities of the programmable logic controllers xe2x80x9cPLCxe2x80x9d and motion functionalities of NC controller can be integrated into a standardized and configurable control system.
The PLC/NC integration takes place in the form of the interconnection of PLC and NC-control assemblies. But, in this design of the integration, an optimum and efficient task structure cannot be obtained for all of the control tasks.
Therefore, the invention is based on the problem of creating optimum instances of the combined PLC/NC control in a simple manner for different control tasks and different initial conditions or requirements of the underlying technical process.
These optimum instances, in principle, are achieved by a consistently configurable run-level model for the control tasks of the combined PLC/NC control. Based on this background, the above-stated problem is solved in that a consistent run level model is formed that has several run levels of various types with different priorities, wherein the following run levels are provided, from greatest to lowest priority:
a) a position-control level, comprising associated clocked system level and user level,
b) an interpolator level, comprising associated clocked system level and user level,
c) an event system level for events requiring a response,
d) a user level for asynchronous errors,
e) an additional user-configurable user level according to user requirements, for alarm and/or event and/or control and/or other periodic tasks,
f) a level group for background processing, formed from a sequence of motion sequences, free cycles and other low-priority system tasks,
wherein the run levels a to e form a level group for real-time processing.
One important advantage of this layering resides in the fact that the communication between the tasks of the process control and those of the motion control is minimized. An additional advantage is that the programming of the control tasks for the process control and for the motion control can be done in a standardized programming language with standardized front-end development tools.
A first embodiment of the present invention is characterized in that the free programmable tasks can each be triggered by signals from the clocked system levels and/or by signals from the event system level. This will assure that the control can respond immediately to an external event, for example.
In an additional favorable preferred embodiment of the invention, additional prioritizing layers are provided within the run levels. The software structure of the combined PLC/NC motion control can be optimized for the different control tasks or for the requirements of the underlying technical process. For example, it is possible to allocate different sources of error to different levels with ascending priority within the user level for asynchronous errors.
In this case it is possible that the priority layers are user-programmable in the user level for asynchronous errors. Thus, the control can be adapted very flexibly by the user for the range of events underlying the application.
In an additional preferred embodiment of the invention, even externally loadable programs can be integrated into the xe2x80x9clevel group for real-time processing.xe2x80x9d Due to this reloading, the desired output control can be dynamically expanded by additional technological functionality.
In an additional preferred embodiment of the invention, the motion sequences, free cycles and other low-priority system tasks can be handled by means of a Round-Robin method in the level group for background processing.
This will ensure that all tasks at this level are handled within a time span defined by the user, and no task at this level will have to wait in vain to be processed.
The essential advantages attainable with the invention include the fact that, due to the potential for parameterization of the run levels by the user, an optimum configuration of the control can be attained for the particular situation. This is because every control problem and every technical process has different requirements in the software implementation within the control system (e.g., quantity of required programs, modules, tasks, number of possible error situations, number of external events that require an appropriate response, complexity of the synchronization). In addition, due to the integration of the process control and the motion control, the communication expense within the control will be drastically reduced.